All 3 Uses of

acquit

in

The Portrait of a Lady

It was Isabel's view that the little girl might have given lessons in deportment to her relative, and nothing could have justified this conviction more than the manner in which Pansy acquitted herself while they waited together for the Countess.
Chpt 35 *

acquitted = handled (conducted or behaved)

Of this refinement of duplicity she presently acquitted him; she preferred to believe him in perfect good faith.†
Chpt 42 *

Definitions:

(1) (acquit as in: she was acquitted)
to officially find "not guilty" of criminal charges

Note that to be acquitted is not the same as being declared innocent of an offense due to the presumption of innocence in the American judicial system. The court determines if there is sufficient evidence to find someone guilty. Some crimes require a lot of evidence for a conviction, so while there may not be enough evidence to declare someone guilty beyond a shadow of a doubt, there also may not be enough evidence to declare a defendant innocent except through the presumption of innocence.
(2) (acquit as in: she acquitted herself well)
to handle oneself in a specified way -- which is typically in a positive way
(3) (meaning too rare to warrant focus)
Much less commonly and archaically, acquit can have other meanings. It can mean to release from a duty, as when Jane Austen wrote "I cannot acquit him of that duty" in her novel, Pride and Prejudice.

It can also mean to perform or complete an obligation, as when Charles Dickens wrote "I have a business charge to acquit myself of," in his novel, A Tale of Two Cities.